In a rear-end collision of a car that occurs when a rear end of your car is struck by another car or when a rear end of your car which is being reversed strikes another car or a construct, a head of an occupant seated on a seat cushion of a car seat would largely tilt back by inertia, and in reaction thereto, the neck of the occupant would likely be given a large shock. With this in view, the car seat is commonly provided with a headrest for receiving the head of the occupant from a back side so as to absorb a shock given to the neck of the occupant in a rear-end collision of the car.
Herein, an occupant seated on a seat cushion and driving a car is, in many cases, postured in an in-seat position with a head slightly apart from the headrest to the front, and many of other passengers not driving the car also have similar in-seat positions. When a car in which an occupant/passenger is seated in such a posture is rear-ended, the head of the occupant would tilt slightly to the rear before being received, and would go tilted back to the front in reaction thereto, so that its benefit of absorbing a shock given to the neck of the occupant would be reduced.
Against this backdrop, there are proposed a vehicle seat and a seat back device which are configured such that in a rear-end collision of the car, an upper body of an occupant tending to move rearward by inertia is caused to subside into a seat back disposed at his/her rear side so that the head of the occupant is swiftly received by the headrest (e.g., see Patent Literatures 1, 2).
A vehicle seat described in Patent Literature 1 includes a pressure-receiving member connected rearward-movably to a seat back frame, as a member for receiving an upper body of an occupant by means of a seat back pad (seat back cushion) within a seat back. A seat back device described in Patent Literature 2 includes a sheet-like elastic member corresponding to the pressure-receiving member described in Patent Literature 1.
In the vehicle seat described in Patent Literature 1 and the seat back device described in Patent Literature 2, the pressure-receiving member (sheet-like elastic member) moves together with the seat back pad to the rear relative to the seat back frame when the rear-end collision of a vehicle causes a rearward motion load to be imposed on an occupant and thus presses an upper body of the occupant against the seat back. As a result, the upper body of the occupant subsides into the seat back, allowing the head of the occupant to be swiftly received by the headrest; in this way, the shock be given to the neck of the occupant can be absorbed.
On the other hand, a vehicle seat having a seat structure in which a side air bag device is provided is generally known (e.g., see Patent Literature 3). The structure disclosed in this Patent Literature 3 is such that an insert wire (tuck-in wire) for attaching a seat skin inside a vertical groove formed in the seat back pad is embedded in a seat back pad.